SA's as a reverse proxy

I have the sinking feeling I already know the answer to this, but without going into really elaborate coding in the resource policies, is it possible to use the SA as a ptp on ports besides 443? Reason I ask is that I have an web base application that allows for secure file transfer to the hosting website. For the most part all communications are conducted via 443, but when there is an upload, a java script gets triggered and redirects the file transfer session to ports 5000-5002.

Here's the kick in the pants, I can't change the application on the inside, nor can I change the ports on the outside.